Gallstone pancreatitis is common and is potentially fatal. Enteral exclusion of bile-pancreatic juice by the stone causes feedback hyperstimulation of the exocrine pancreas that induces pancreatic overproduction of acute inflammatory mediators. Systemic spread of acute pancreatic inflammation leads to multi-organ failure which is the major cause of death from acute pancreatitis. However, no specific treatment is currently available as the pathogenic mechanisms are not well understood. We have used the rodent model of duct ligation-induced acute pancreatitis as an experimental analogy to investigate disease pathogenesis. We acknowledge the fact that species-related variations between rodents and humans may limit the clinical relevance and potential applications of these findings. However, useful information can still be garnered from these studies. Using a unique and original surgical model, the Donor Rat Model, we showed that enteral bile-pancreatic juice replacement substantially ameliorates pancreatic morphological changes in the early stages of ligation-induced acute pancreatitis and inhibits pancreatic overproduction of acute inflammatory mediators. We concluded that bile-pancreatic juice exclusion from gut plays an important role in exacerbating acute pancreatitis in our experimental model. Using our donor model, we have shown that stress kinase activation in pancreata of rats and mice after duct ligation is ameliorated by duodenal bile-pancreatic juice replacement. We present new evidence that p38 and ERK regulate NFkB-mediated gene transcription in an exocrine pancreatic (AR42J) cell line. Furthermore, we show that 24 h of duct ligation in the mouse is associated with pulmonary ERK activation and acute lung injury. We hypothesize that the local and systemic acute inflammatory response in gallstone pancreatitis is worsened by the enteral exclusion of bile-pancreatic juice that causes feedback hyperstimulation of the exocrine pancreas to activate pro-inflammatory pathways in the presence of an obstructed duct. Aim 1: To determine the mechanism of activation of pro-inflammatory pathways in isolated pancreatic acinar cells. Aim 2: To determine the mechanism of pancreatic production of cytokines, chemokines, and reactive oxygen species in the early stage of ligation-induced acute pancreatitis. Aim 3: To determine the mechanism of development of the local and systemic inflammatory response in the late stage of ligation-induced acute pancreatitis. We use novel approaches, such as in vivo gene modulation, to investigate mechanisms of disease pathogenesis by inhibition of ERK and p38. A role for enteral bile-pancreatic juice exclusion in the pathogenesis of gallstone pancreatitis, and the systemic inflammatory response syndrome, may provide the rationale for much needed therapeutic initiatives for a condition that is associated with considerable morbidity and mortality - and for which no specific therapy is known. PUBLIC HEALTH RELEVANCE. Acute pancreatitis is a common inflammatory condition of the pancreas that is potentially fatal. The commonest cause of acute pancreatitis world-wide is gallstones. This research proposal investigates how gallstone obstruction of the pancreatic duct may initiate acute inflammation of the pancreas. A better understanding of these processes will help to improve the treatment of this potentially fatal condition.